Equiv. Parts: 2SD669, 2SB649

Does anyone know of equivilent part numbers for the following:

* Hitachi 2SD669
* Hitachi 2SB649

BTW, the package is a TO-192...

Here is a link to the datasheets.

The circuit designer, Randy Slone, told me that some people replaced them with components from the MJE series but he couldn't remember the part numbers. I believe they are made by motorola but I cannot find any datasheets.

Any help would be GREATLY appreciated!
Thanks in advance!!!
Well done!!! I didn't see that...

The reason I went for this design is:


(The Audiophile's Source Book pg172)Finally, we come to Fig. 6-21, which is my favourite audio power amplifier design of any type .

and I'm sure he's built alot of amplifiers! THD+N is 0.04% but usually more like 0.005% and BW is 3Hz to 120kHz! The SNR is over -115dB...I don't claim to understand what Signal to Noise Ratio is when measured in dB...I thought that a ratio had no units but there you go!

Anyway...I'll have a look for UK suppliers of the MJE344 and MJE350...


I have only checked what is available from swedish suppliers, but the closest match I have found are the Toshiba devices 2SA1837
and 2SC4793, which I think should work fine.

I recommend against the suggested Motorola/ON devices
MJE344 and MJE350. Compared to the orignal devices, 2SB649
and 2SD669, they seem quite inferior.
1) A min. fT of only 15MHz, compared to 140MHz
2) Max. IC is 500mA, compared to 1.5A
3) Wider spread in hFE and much lower min hFE
4) They seem not even to be complementary devices.
They would probably work in any of Sloanes amplifiers, but so
would problably a number of other BJTs having similar specs.

Why do you want a replacement, BTW? Admittedly 2SB649 and
2SD669 tend not to show up in every suppliers stock, but
decent replacements seem at least as rare, in my experience.
If you search for the part numbers with Altavista or Google, you
will find quite a number of European suppliers of these devices,
some of them most certainly in the UK.

BTW, Spice models for 2SB649 and 2SB669 would be most
Randy didn't say which of the MJE series his friends crossed to, but since ON Semi said that the MJE350 and 344 are compatible (or will even just do) then that's fine by me...They are sending out 20 of each on a sample order!!!

That just makes it even better! 40 free...I don't build amps often so that'll last me a long time!


I have checked a number of different manufacturers compatibility
recommendations, and they were all questionable.
The problem is that SB649/SD669 are rather
special devices and not many manufacturers have something
similar. It seems that they basically try to find a device that
is "safe" to use, ie. greater or equal VCE, IC and power rating,
and do not care much about other properties. Obviously, ON
does not even make sure that the IC rating is sufficient.

It will most likely work to use the suggested ON devices in
any of Sloanes amplifiers, but be prepared that tech. specs.
and sound quality may be inferior. To what extent is probably
hard to predict though.

Anyway, go ahead and use the ON devices if you want to
give them a try. If it sounds good, be happy, otherwise, try
to get hold of better devices. Just make sure that you don't
need the higher IC rating in the particular design your building.
I remember quite a while ago i emailed Randy Slone with the same problem, ie. I couldn't source the Hitachi 2sd669/2sb649 bjt's and his reply was...

"There isn't anything "super special" about the 2SD669/2SB649 devices. You should be able to obtain equal results from several devices in the "MJE" line - just try to match the Hfe, Ft, and Pd parameters fairly close, and the performance should be equal. "

(hope Randy doesn't mind me quoting him, hehe)
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I agree there is nothing "super special" about SB649/SD669
except the particular combination of essential parameters.
The problem is to find a close match for all of these. I just
tried the parametric search at ON semi again, to see if I had
missed some possible replacement in my earlier searches, but
it seems I hadn't. Assuming we want a min VCE >= 150V and
IC >= 500mA, there is only MJE 344 and some similar devices
for even higher voltages (I only bothered checking for NPNs).

The most problematic parameter is fT, which is about 10% of
the value for SD669. I don't know how much difference this
will make in practice, but it is one of the parameters Sloane
list as crucial ones for a driver. Also, looking at similar japanese
devices designed for driver stages, they typically have a high
fT. I guess this all boils down to the old discussion of how much
bandwidth is needed in an amplifier. Most certainly there is
quite a lot of expensive and good-sounding amplifiers on the
market using drivers similar to MJE344/350.

Actually, when rechecking my local supplier, I just realized that
MJE340 seems more similar to MJE350, than MJE344 does. This
also made me recheck the datasheets and there is no spec. for
the fT value at all for MJE340/350. That is why I had dismissed
these devices and forgotten about them.
2sd669/2sb649 source

A: MCM carries these. Or at least it did once. It now appears to be part of Newark -- so who knows?

B: I built a rather low powered version of one of Slone's amps to squeeze into a small box under my PC monitor to drive a set of small speakers. If you discount my fumblings and goofs, it was quite straight forward. I had access to an older distortion analyzer (measures down to .003%) and was unable to even get a reading in the audible spectrum until 20kHz, --which has been inauible to me for the last couple of decades! I'm working on higher powered version presently.
Alternative ? Maybe?

I just happened to notice the Zetex "Super E-line" page in the Digikey catalog. Going strictly by the basic numbers, some of these could sub for 2sb649/2sd669. However, they are a modified to-92 package which leads me to wonder if there is more at issue than just the basic specs.

if you need to heatsink them you would need to be a little creative since the package isn't even stanadrd TO-92 - kind of squished flat. Also a little pricey.
I think I found good replacements, what sayest thou?

I agree with other on the board about the MJE series from On- Semi. Looks to be a far stretch.

How about these replacements from Zetex? They have equivalent SPICE models. :nod:

Hitachi NPN 2SD669 replacements :
Zetex ZTX1055A or ZTX1056A

Hitachi PNP 2SB649 replacements :

What do you think? All the parameters seem pretty close


P.S. For those who don't know that data for these, www.Zetex.com for the Zetex BJTs and Hitachis stuff can be found in the diyaudio archives.
I spent several hours on an extensive web search. I've concluded there are not any official models. Some Spice software (but not the free ones) have modules that will try to build a model from datasheet info. If someone on the forum has that capability maybe they would be kind enough to plug in the data sheet info andshare the result.